Background: The significance of occult hypoperfusion (OH) in the development of respiratory complications (RC), multiple system organ failure (MSOF), and death, and the effect of rapid identification and correction of OH in the severely injured trauma patient was investigated.
Methods: A pilot retrospective study and the analysis of a prospective protocol to correct OH were performed. Pilot study: all trauma patients admitted to our Level I trauma center between February and December of 1995, who survived greater than 48 hours, had an Injury Severity Score greater than or equal to 20, and intensive care unit stays greater than 48 hours were evaluated. Prospective study: patients admitted between January 1, 1996, and April 30, 1997, who survived greater than 24 hours, with Injury Severity Score greater than or equal to 20, and who were hemodynamically stable (systolic blood pressure greater than 100, pulse rate less than 120, and urine output greater than 1 mL/kg per hour) were included. Serum lactic acid (LA) levels were measured at arrival and at proscribed intervals. In the pilot study, initial LA levels were examined in relation to outcome and complications. In the prospective study, patients with two consecutive LA levels greater than 2.5 mmol/L underwent invasive monitoring and vigorous resuscitation to correct their lactic acidosis.
Results: Among the 31 patients studied in the pilot study, there were 4 deaths, 6 cases of MSOF, and 13 patients with RC. Lactic acidosis and poor cardiac performance, as evidenced by low cardiac index (CI) with normal filling pressures, were seen in all cases of MSOF and RC, as well as in all deaths. From these results, the prospective study was performed. Eighty-five intensive care unit patients met criteria for inclusion in the study. Six additional patients were excluded because of severe, untreatable intracranial hypertension at admission to the intensive care unit. Fifty-eight of these patients had OH in the first 24 hours. Forty-four patients corrected their OH within 24 hours with vigorous resuscitation. There were no deaths, three cases of MSOF, and 10 cases of RC in those patients who corrected OH within 24 hours. Persistent OH (>24 hours) was seen in 14 patients, despite resuscitative efforts, 43% of whom died. MSOF and RC were present in 36% and 50% of cases, respectively (p<0.05).
Conclusion: Initial lactic acidosis is associated with lower cardiac performance and higher morbidity and mortality. Persistent OH is associated with higher rates of RC, MSOF, and death after severe trauma. Early identification and aggressive resuscitation aimed at correcting continued elevation in serum lactate improves survival and reduces complications in severely injured trauma patients.